In the state of the art solenoids of this kind are sufficiently known, for example for operating valves. The range of use of the valves is often very different. They are used, for example, for controlling aggressive media flows (liquid or gas). What is often undesired here is that the aggressive medium (for example soiling in the medium, changed viscosity, the medium to be controlled is chemically incompatible with the material of the magnet, for example it dissolves it) gets in the armature space. Therefore, it is known to fill the armature space with defined liquid, and to provide a boundary element at a suitable point between the armature space and the valve space. In the state of the art a separating membrane is used as boundary element. By filling the armature space with an armature space liquid the pressure of the membrane is compensated, and the possibly considerable pressure stress of the solenoid (this may be, for example with hydraulic application cases, up to 200 bar and more) does not have any influence on the compressive strength of the solenoid.
In the known solutions the essentially disc-like separating membrane is fastened, on the one hand, to the tappet, and radial on the outside at the magnetic core, in particular in the tappet boring. The movement of the tappet, that is, on the one hand, caused by the electro-magnetic effect (the wire windings of the coil, flown through by electricity, generate a magnetic field that moves the armature in the armature space, and this movement is transferred to the tappet, or the restoring movement is carried out, for example, by a pole reversal of the solenoid, or by suitable mechanic elements, for example, a readjusting spring or the like), is here essentially rectangular to the plane, disc-like arrangement of the separating membrane. The stroke of a few tenths of millimeters, millimeters or up to 5-8 millimeters caused by the armature or tappet then has also to be carried out by the separating membrane in a suitable way, leading to a corresponding mechanic stress of the separating membrane. The known separating membranes consist here of elastic material, and it can be seen that the maximum deformation forms in the area of the smallest radius or the smallest cross section in the separating membrane, that means, the separating membrane is considerably stressed in particular in the fastening area at the tappet by a hinge-like movement. Furthermore, it has to be taken into consideration that the tappet movement is derived from the armature movement (the tappet is, for example, connected fixedly with the armature, or mounted floating on it with appropriate readjusting elements), and exchanging the tappet from the interior of the solenoid leads to a volume compensation in the armature space and the tappet boring necessarily connected with the armature space. This relative change of volume has to be compensated accordingly by the boundary element and leads to a compensation movement of the separating membrane. In the known arrangements the armature movement and the compensation movement of the separating membrane is in opposite direction. This leads to a considerably additional mechanic stress of the separating membrane by shearing forces leading to a significant reduction of the life, on the one hand, or to a restriction of the possible stroke, on the other hand.
Referring to this state of the art, it is the object of the present invention to overcome at least one of the before-mentioned disadvantages.